Apparatus for monitoring the temperature preveailing in a grate of the type used for drying and calcining shapes



Aug. 27. 1968- SCHMHSER ET AL 3,398,941

APPARATUS FOR MONITORING THE TEMPERATURE PREVAILING IN A GRATE OF THE TYPE USED FOR DRYING AND CALCINING SHAPES Filed March 28, 1967 2 Sheets-Sheet 1 3s-- v f 5 f6 Aug. 27. 1968 SCHMElSER ET AL 3,398,941

APPARATUS FOR MONITORING THE TEMPERATURE PREVAILING IN A GRATE OF THE TYPE ussn FOR DRYING AND CALCINING SHAPES Filed March 28, 1967 2 Sheets-Sheet 2 G R/kTE SPEED CONTROL United States Patent 12 Claims. ((21. 263-28) ABSTRACT OF THE DISCLOSURE The temperature prevailing on the forward band of a sintering grate and varying within a range defined by an upper and a lower limiting value is monitored by means of a control impulse initiated when the upper or lower temperatures are found to be beyond the limiting values, the control impulse produced causing adjusting means to be moved automatically from a neutral central position to a position antagonistic to the temperature deviation and, after correction of the temperature, to be returned to the neutral central position.

The present application is a continuation-in-part of application Ser. No. 465,909, filed June 22, 1965, now US. Patent 3,343,823, and relates to an apparatus for automatically monitoring the temperature prevailing in the thermally most highly stressed portions of a sintering grate used for drying and calcining pellets.

As taught in German specification No. 1,167,317, the apparatus to be monitored comprises two conventional travelling grates connected in series, where the second grate travels through a cooling zone, whereas the first travelling grate, which serves as a sintering grate, travels successively through a drying zone, a calcining zone and a sojourn/hardening zone, each zone comprising at least one chamber.

As described in German specification No. 1,189,053, the individual chambers are separated from each other by interposed partition walls, which serve to improve the spacing of individual zones and to permit more exact flow of exhaust gas, hot gas and issuing gas, and the sojourn/hardening zone has associated shutoff and control means which alternatively enable, by means of a blower, exhaust gas coming from the calcination zone to be suction drawn across a layer of sinter material, as the calcination thereof proceeds-this means a temporary desirable enlargement of the volume of the calcining zone-or enable the removal of exhaust gas to be arrested, or enable hot air coming from the cooling zone to be injected by means of :a blower cooling the chain to be injected into the suction chamber against the forward band of the sintering grate for the purpose of cooling.

US. Patent 3,343,823 describes a method and apparatus for monitoring the temperature prevailing in a sintering grate, wherein the radiation emitted by the underside of the grate plates forming part of the forward band of the sintering grate is continuously and quantitatively determined by infrared radiation testing and evaluated, the determination and evaluation serving as an index of the temperature prevailing on the said grate plates across the whole width of the sintering grate.

The present continuation-impart relates to an apparatus for automatically monitoring the temperature pre- 3,398,941 Patented Aug. 27, 1968 vailing on the forward band of a sintering grate, the said temperature varying within a range defined by an upper and a lower limiting temperature value.

The apparatus of the present invention comprises adjusting means for determining the temperature adjustment, for example a valve or damper. The adjusting means is maintained, in a neutral central position as long as the temperatures prevailing in the grate are found to be within the range defined by the said upper and lower limiting values, respectively, the adjusting means being arranged so as to respond to a control impulse produced when the upper and lower temperatures, respectively, are found to be beyond the limiting values, the control impulse produced causing the adjusting means to be moved automatically from the neutral central position to a position antagonistic to the temperature deviation, and, after correction of the temperature, to be returned to the neutral central position.

The adjusting means determining the primary generation of heat and the supply of combustion gas, primary and secondary air are arranged to respond to a control impulse produced when the upper and lower temperatures, respectively, are found to be beyond the limiting values, the said control impulse causing the said adjusting means to be set automatically to a position antagonistic to the temperature deviation. In the event that the upper limiting temperature is found to have been exceeded, the temperature prevailing in the grate can be influenced primarily by diminishing the quantity of hot gas supplied to the calcination chambers, i.e. by the simultaneous controlled reduction of the quantity of combustion gas and the quantity of primary and secondary air supplied. This means that the amount of heat generated inside the calcination chambers is adapted to the reduced need of calorific energy. Inversely, when the temperature is found to be below the lower limiting value, the quantity of heat available can be increased by increasing the amount of exhaust gas (controlled escalating adjustment of the burners).

The temperature can furthermore be monitored by so arranging the throttle valves, which are disposed below the sintering grate and suction draw exhaust gas from the sojourn hardening zone, that they respond to the control impulse produced when the temperature is found to be beyond the upper or lower limiting value, the control impulse produced causing the said throttle valves to be opened or closed automatically, whereby, when the upper limiting temperature has been exceeded, additional amounts of relatively cool hot gas coming from the cooling zone can be injected, within the region of the sojourn/hardening zone, to arrive below the sintering grate, the suction removal of exhaust gas being then arrested.

In this manner, the calcination can be made to take place at a higher or lower level inside the layer of pellets, which means that the temperature distribution in said layer of pellets and the layer covering the sintering grate can be produced as desired (of. German Patent 1,167,- 317).

The flow of exhaust gas by suction-drawing it more or less intensely through the layer of pellets within the sojourn/hardening zone results in the geometrical size of the calcination zone being effectively modified. More intense suction flow means an enlargement of the calcination zone, of which the end is thereafter found to reach into the sojourn/hardening zone, i.e. the active suction area of the calcination zone is enlarged. The exhaust gas supplied at increased rates, due to controlled escalating adjustment of the burners, is thereby offered an enlarged suction area with only a slight change in the specific thenmal load (kcal./square meter-hr.) found to prevail on the sintering grate.

In the event that the sintering grate is so operated that no exhaust gas is suction-removed below it in the region of the sojourn/hardening zone, the said grate is found, when the upper limiting temperature has been exceeded, to be cooled by the automatic injection of hot gas coming from the cooling zone.

In accordance with a further feature of the present invention the sintering grate is arranged to respond to a control impulse produced when the upper and lower temperatures, respectively, are found to be beyond the limiting values, with the result that the travel velocity of the sintering grate is increased or reduced. In other words, the momentarily needed calorific energy is adapted to the amount of heat generated in the calcination chambers.

The adjusting means used in the present invention can be coupled together and arranged so as to perform the various steps jointly or successively, e.g. the step of adjusting the throttle valves or other valves and the step of varying the travel velocity of the grate.

In the case of automatic monitoring, where the control impulses are produced at an upper and a lower limiting temperature, respectively, the temperature prevailing in the sintering grate may be found to vary for some time within the range defined by the said upper and lower limiting temperature values. As set forth above, this can be avoided by associating with each individual adjusting means a neutral central position adapted to respond to a control impulse. This control impulse causes the said adjusting means to be moved in the desirable direction from the neutral central position towards a final position, as long as the temperature is found to be beyond the upper or lower limiting value, and thereafter to be returned automatically to the neutral central position. In this manner, it is ensured that the sintering grate is operated under identical conditions when no control impulse has been produced. This is a factor of decisive importance for the operation of the sintering grate under mild (i.e. noninjurious) conditions and for the quality of the sintered material.

The adjusting means are arranged to be actuated continuously. However, in order to enable a sintering grate to be adapted to the conditions prevailing at a given time, the adjusting means should permit stepwise adjustment. This can be achieved by means of separate step impulse initiators producing the control impulses when the temperature is found to be beyond the upper or lower limiting value. These step impulse initiators with their varying action and stop intervals enable the sintering grate to be heated or cooled at optimum velocity and the control action to be adapted to the magnitude of the temperature deviation.

As taught in US. Patent 3,343,823, two test points are connected to one another in the direction of motion of the sintering grate forward band, each test point comprising two control means arranged in opposite fashion and monitoring the temperature radiation. In the present case, the two control means monitoring the upper limiting temperature radiation are set to a so-called or function, and those monitoring the lower limiting temperature radiation are set to a so-called and function. Applied to the first case, this means that a control impulse is produced when only one of the two control means arranged opposite to one another and monitoring the temperature radiation indicates the upper limiting temperature to have been exceeded anywhere across the width of the sintering grate. In the second case, to produce a control impulse, the two control means monitoring the temperature radiation are both required to indicate that the lower limiting temperature has been reached across the grate crosssectional area they monitor.

An apparatus suitable for use in carrying out the present invention is shown in the drawing wherein FIGURE 1 is a diagrammatic view of an apparatus according to the present invention, and FIGURE 2 is a sectional view of a 4 sintering grate arrangement with infrared radiation-sensitive pick-up means disposed opposite one another.

Control means 1 and 2 are connected adjacent a sintering grate for monitoring the temperature of the grate. The control means are set to produce control impulses when the temperature of the grate is outside a predetermined range. r

The initial state is assumed to be that at which no control impulse, such as normally initiated when the upper or lower temperature is found to be beyond the limiting temperature values, is produced. The adjusting motor 7 stands still and the throttle valve 8, which should be mentioned as the simplest adjusting means, is held in neutral central position 9, 12.

The control impulse produced when control means 1 monitoring the temperature radiation indicates that the upper limiting temperature of the predetermined range has been exceeded, causes the adjusting motor 7 to be started by means of a switch group 3.

Throttle valve 8 is arranged to be closed by the running motor until the latter is switched off by terminal switches 10, 13 through switch group 3. Throttle valve 8 is then found to remain in closed position.

When the control impulse disappears, switch gnoup 4 causes the adjusting motor 7 to be started again but to be driven in inverse direction so as to open throttle valve 8, until the motor is switched off by terminal switch 9. The throttle valve 8 is found to have returned to the neutral central position.

The control impulse initiated when control means 2 monitoring the temperature radiation indicates that the lower temperature is beyond the lower limiting value, causes the adjusting motor 7 to be started by means of switch group 6 and throttle valve 8 to be opened by the running motor until switched off, with the throttle valve opened, by terminal contact switches 11, 14.

When the control impulse disappears, switch group 5 causes the adjusting motor 7 to be started again, but to be driven in inverse direction so as to close throttle valve 8, until the motor is switched oif by terminal switches 9, 12. The throttle valve 8 is then found to have returned to the neutral central position.

The throttle valve 8 is arranged to move continuously between the open and closed positions. It is, however, possible as mentioned above to make the throttle valve 8 move stepwise by associating with the switch groups 3 to 6 an orthodox step-by-step system with adjustable action and stop periods.

The switch groups 3 to 6, which need not be discussed in the absence of particular characteristic features, can be assembled in customary manner from electromechanical and/or electronic constructional elements in accordance with recognized systems of designing circuits.

FIGURE 2 illustrates one of the throttle valves 8 arranged in a conical-shaped suction tube 20 laterally disposed between the upper and lower belts of the apparatus according to the present invention. Such an arrangement permits varying quantities of air or gas to be suctiondrawn through the layer of material supported by the upper belt of the apparatus. When small volumes of air or gas are suction-drawn through the material the temperature of the material is significantly lower than the temperature of the material when large volumes or air or gas are suction-drawn through it. Thus, the temperature of the material being processed is readily regulated by appropriately opening or closing the throttle valve 8.

The control impulses from the control means 1 and 2 can also be connected to cause the sintering grate to automatically travel at an. increased speed when the upper limit of grate temperature is exceeded. Conversely, when the grate temperature is lower than the lower limit of the predetermined range the control impulses cause the grate to automatically travel at a reduced speed. FIGURE 2 illustrates a speed control unit connected to adjust the speed of the sintering grate so that grate temperature is maintained within a predetermined range.

We claim:

1. In the combination of a traveling sintering grate formed of a drying zone, a calcining zone and a sojourn/ hardening zone, the grate being of the type used for drying and calcining shapes, and a device for measuring and controlling the temperature of the grate, the device consisting of two coplanar infrared radiation-sensitive pick-up means disposed directly below and adjacent to the grate in opposite relationship to one another, one pick-up 'means being disposed on the left hand side and the other disposed on the right hand side seen in the direction of motion of the sintering grate, and each pickup permitting overlapping control of half the Width of the sintering grate nearest thereto, the improvement according to which comprises associating with the infrared radiation-sensitive pick-up means an adjusting means for automatic adjustment of the grate temperature whereby the adjusting means is arranged (a) to respond to control impulses initiated by the infrared radiation-sensitive pickup means when the temperature prevailing in the grate is outside a predetermined range, (b) to remain in a central position as long as the grate temperature is within the predetermined range and no control impulse is produced, (c) to be moved by the control impulses produced by the infrared radiation-sensitive pick-up means when the grate temperature is outside the predetermined range, from the central position to a position antagonistic to the temperature outside the predetermined range, and (d) to return to the central position after correction of the grate temperature when the infrared radiation-sensitive pick-up means cease to produce further control impulses.

2. The combination of claim 1 wherein the adjusting means is connected to control the supply of combustion gas to the grate.

3. The combination of claim 1 wherein the adjusting means is connected to control the supply of primary air to the grate.

4. The combination of claim 1 wherein the adjusting means is connected to control the supply of secondary air to the grate.

5. The combination of claim 1 wherein the adjusting means comprises throttle valves for suction-drawing exhaust gas from the sojourn/hardening zone arranged to respond to the control impulses produced by the infrared radiation-sensitive pick-up means when the grate temperature is outside the upper limit of grate temperature, the valves being moved by the impulses from their central position to closed position whereby the removal of exhaust gas is arrested.

6. The combination of claim 1 wherein the adjusting means comprises throttle valves for suction-drawing exhaust gas from the sojourn/hardening zone arranged to respond to the contnol impulses produced by the infrared radiation-sensitive pick-up means when the grate temperature is below the lower limit of grate temperature, the valves being moved by the impulses from their central position to open position.

7. The combination of claim 1 wherein the sintering grate is arranged to respond to the control impulses produced by the infrared radiation-sensitive pick-up means when the upper limit of grate temperature is exceeded, the control impulses causing the grate to automatically travel at an increased speed.

3. The combination of claim 1 wherein the sintering grate is arranged to respond to the control impulses produced by the infrared radiation-sensitive pick-up means when the grate temperature is lower than the lower limit of the predetermined range, the control impulses causing the grate to automatically travel at a reduced speed.

9. The combination of claim 1 wherein a pair of infrared radiation-sensitive pick-up means are connected to monitor the upper limiting temperature of the grate so that a control impulse is initiated by either pick-up, and wherein a pair of infrared radiation-sensitive pick-up means are connected to monitor the lower limiting temperature of the grate so that a control impulse is initiated only when both pick-ups sense a temperature below the lower limiting temperature of the grate.

10. The combination of claim 1 wherein the adjusting means are coupled together to be actuated automatically.

11. The combination of claim 1 wherein the adjusting means are arranged to be actuated continuously.

12. The combination of claim 1 wherein the adjusting means are arranged to be actuated stepwise by associated step impulse generators with varying action and stop periods for either of the directions of motion of the adjusting means.

References Cited UNITED STATES PATENTS 2,070,300 2/ 1937 Smith 26621 3,100,106 8/1963 Bielenberg et a1. 26328 X 3,149,192 9/1964 Schuerger et a1. 26328 X 3,211,441 10/1965 Mikakawa et al 236--15 3,259,381 7/1966 Walker 26328 X 3,275,431 9./l966 Sawada 266-21 JOHN J. CAMBY, Acting Primary Examiner. 

